On June 6, 1944, 177 men under the command of Philippe Kieffer landed in Normandy within the British beach section called Sword. The “Kieffer Commando” was the only French unit to be engaged that day in Operation Overlord. Fated to be remembered in the collective memory only as the “Frenchmen of D-Day,” Kieffer's men were to see, after that summer, the story of their action largely cut off, forgotten or misrepresented. This article examines this “memory lapse” by seeking the real identity of the French battalion, from its formation in 1942 up to its disbanding in July 1945: a military unit involved in raids in 1943 and in combat in the Netherlands and Germany in autumn 1944 and at the beginning of 1945. Central to this study is the figure of the leader who founded the Commando, the “civilian in uniform” who was to bequeath to the French Navy the structure of its future commando squads and would give his name to the 6th Marine Commando, created in 2008. Finally, the article examines the ways in which the “Kieffer Commando” has been recorded in the various annals of the British, the Free French, and the French Navy.